When comparing Opa vs Haxe, the Slant community recommends Haxe for most people. In the question“What are the best languages that compile to JavaScript? ”Haxe is ranked 5th while Opa is ranked 27th. The most important reason people chose Haxe is:

Haxe allows you to develop for Web, iOS, Android, Blackberry, Windows, OSX, Linux and others, all at once, without the need to switch languages and maintain separate code bases.
This is possible because Haxe can compile to JavaScript, ActionScript, Flash AVM bytecode, C++, Neko, PHP, C# (.NET) and Java.
Support for even more platforms and languages is under development.

Pros

Pro

Type Inferred

Opa uses type inference to decide what code runs on the client or the server, so you can organize code how you like, but still be sure that it runs where it needs to.

Pro

Familiar Javascript Syntax

Opa's syntax is very similar to JavaScript, making it an easy choice for developers who are used to developing in JavaScript.

Pro

Client and Server in the same language

Pro

Compiles to multiple platforms and languages

Haxe allows you to develop for Web, iOS, Android, Blackberry, Windows, OSX, Linux and others, all at once, without the need to switch languages and maintain separate code bases.

This is possible because Haxe can compile to JavaScript, ActionScript, Flash AVM bytecode, C++, Neko, PHP, C# (.NET) and Java.

Support for even more platforms and languages is under development.

Pro

Powerfully expressive but easy to learn

The language was designed to be very expressive with the smallest possible amount of syntactic sugar. There are actually fewer keywords than other languages with similar power.

Pro

Pick up errors at compile time

One big advantage over pure javascript, (or some other languages listed here) is that Haxe will pick up a whole range of errors when you compile, saving you the pain of having to try and debug them later. This includes everything from syntax errors ("Unexpected ;") to type errors ("Class user has no field username. Suggestion: username").

Pro

First class code completion

Code completion is built into the compiler and available to the IDE allowing for much smarter code completion that can actually parse and understand the syntax tree.

Pro

Code reuse server side and client side

You can use the same classes on the server as you do on the client where applicable. This saves a lot of time.

Pro

Syntactic macros

Syntactic macros allow you to extend compiler features at the syntax tree step. Macros come into play after code is parsed into the abstract syntax tree, and macros allow you to transform it before the rest of the compilation completes.

This provides for immense power, while at the same time scoping the extensibility at a level that is powerful, but well constrained.

Pro

Extremely fast compilation

Haxe can easily compile over 100,000 lines of code to JS in seconds on a mid-spec computer.

Pro

Ability to use existing JS libraries

Haxe has the ability to use "externs". These are haxe files which describe the usage of existing JS libraries. Get code completion and compile-time-checking for everything from jQuery to Node.js.

Even without externs, native JS code can still be used through untyped code.

Pro

Powerful type inference with strong typing

After a type is inferred from its context, it cannot be changed to a new type, and type safety is done at compile time so it stays safe without the extra maintenance required for static typing.

Pro

Similar to JavaScript and ActionScript 3

The language is very easy to learn for those with background in JavaScript or ActionScript 3.

Pro

Large library support. From servers to games.

Haxelib (common library repo) and other sources contain large codebases for anything from cryptography to communications. A lot of these are fully cross platform and work with the JavaScript target.

The JavaScript target can be used for everything from node.js server applications (with code completion) to games using either the Flash-like OpenFL library or direct canvas or WebGL programming.

Pro

Small, readable output

The output that is generated can be trimmed using "dead code elimination" to only include those functions and libraries that are strictly necessary. All code is very readable with only minimal extras for specific functionality.

Small output is good for frontend development as file size is a major concern.

Pro

Algebraic data types and pattern matching.

Pro

Established project

Haxe has been around for more than 10 years (since 2005) and whilst not the most popular project, has had continuous growth.

Highly unlikely to disappear or for support to stop.

Pro

Friendly community

Friendly community

Pro

Offload execution to the server with remoting

Using a remoting proxy you can get type safe server to client communications, allowing for remote method execution on the server as if they were part of the client side code.

Pro

Package management like Java

Package tree is just directory tree, it's wonderful!

Pro

Available in NPM

Pro

Create without needing to be limited to a language, target, or commercial ecosystem

Pro

Builtin conditional compilation support

Haxe supports conditional compilation, so depending on compiler flags Haxe will include or exlcude sections of your code. Making it easy to have debug and release builds.

Pro

Abstract enums allow constants with exhaustiveness check

You can define constants in an abstract enum and when used in a switch/case statement Haxe checks for exhaustiveness, making sure every constant is covered - with no runtime implication.

It's not easy to convince people it's as good as it really is unless you can get them to really try it

Alternative Products

Each month, over 2.8 million people use Slant to find the best products and share their knowledge. Pick the tags you’re passionate about to get a personalized feed and begin contributing your knowledge.